This invention relates generally to evaporative air coolers. More particularly, the present invention relates to efficient, generally upright and compact evaporative air conditioning units designed for residences, offices, or the like.
Evaporative air coolers are well known in the prior art. Typical evaporative coolers intake ambient air and pass it through a wetted pad to provide cooling. When water evaporates, heat is removed from the air in quantities related to the latent heat of vaporization. Cooling is proportional to a variety of well known factors such as air temperature, the relative humidity, the wet bulb depression, air speed, water temperature and other factors. A variety of absorbent mats such as trickle pads and excelsior pads have been employed in the art. A suitable inlet provided in a typical evaporative cooling unit admits air into the system in response to fan system suction. The air stream is routed through the water absorbent mat and is cooled by evaporation. As the air is cooled its humidity increases according to well known principles. Of course water must be periodically added to evaporative coolers to keep them functional.
Evaporative coolers are particularly useful in areas of relatively low humidity, which are characterized by relatively high wet bulb depressions. Wet bulb depression is calculated by subtracting the wet bulb temperature of ambient air from the dry bulb temperature measured at substantially the same time. In an evaporative air cooler air temperature is lowered when the latent heat of vaporization of water is extracted from the air according to well known principles. However, the efficiency of conventional evaporative coolers is normally in the area of fifty-five to sixty-five percent. The closer the unit's measured output air temperature is to the wet bulb temperature of untreated ambient air, the greater the achieved efficiency. Of course in an evaporative air cooler the output air theoretically cannot be cooled more than the wet bulb point. The amount of cooling is then divided by the depression, and the result is multiplied by 100 percent. By way of example, if the observed depression is ten degrees, and the air exiting the cooler has been cooled six degrees, then that device has exhibited an efficiency of sixty percent.
U.S Pat. No. 4,026,971 issued May 31, 1977 to Glascoe discloses a "round" evaporative cooler having a circular evaporation pad surrounding a blower. Air drawn into the apparatus through the pad is forced downwardly through the discharge mouth of the fan. Another cylindrical evaporative cooler is seen in U.S. Pat. No. 4,428,890. This device discloses a round or cylindrical evaporative cooler having a somewhat circular porous pad for distributing water. Another "cylindrical" evaporative air cooler is seen in U.S. Pat. No. 4,428,890 issued to Harrell on Jan. 31, 1984. Engel U.S. Pat. No. 3,975,470 issued Aug. 17, 1976 replaces the well-known prior art "cylindrical" water pad with a generally elongated and rectangular evaporator pad.
Goettl U.S. Pat. No. 3,400,185 discloses a generally cubical evaporative cooler in which a motor-driven fan is disposed interiorly of the cubical enclosure, and which draws air in through a generally horizontally disposed, rectangular pad. Air drawn through the pad is forced outwardly through a peripheral, open mesh grill. U.S. Pat. No. 4,452,615 issued June 5, 1984 discloses an air conditioning system in which a squirrel cage system disposed interiorly of a rigid enclosure draws air through a plurality of parallel filter media for cleaning and then humidifying the air. U.S. Pat. No. 4,029,723 issued to Morrison on June 14, 1977 discloses an arrangement of panels which inter-fit together to aid in the manufacture of the device.
A variety of different evaporative coolers have been suggested previously for vehicles. Generally rectangular systems are numerous, and a variety of generally cylindrical or "round" designs exist as well. Known evaporative air coolers may direct the air flow through horizontally disposed, generally planar water absorbent pads, through rectangular, vertically disposed pads, or through curved, encircling pads. The air may be drawn into the cooler and forced outwardly through peripheral side walls, or the process may be reversed, drawing the air in through the side walls and out through ducts which penetrate the side walls. Ducts may also be colinear with the axis of the shroud.
Representative of automotive evaporative coolers is U.S. Pat. No. 3,372,911 issued to Herboldsheimer on Mar. 12, 1968. The latter unit is adapted to be mounted upon the roof of a cab of a vehicle and is designed to handle dust and the shifting of water in response to vehicle movement. Representative of typical automotive evaporative coolers is U.S. Pat. No. 3,552,097, issued Jan. 5, 1971. The latter apparatus may be mounted in the top of a vehicle cab or the like. Air is drawn in through the periphery of the shroud by a rotating fan, and it is forced into the motor plenum through a radially surrounding peripheral filter. Processed or cooled air is thus forced out through the filter, and means are provided to circulate the water from a lower reservoir up into the filter region.
Nagele U.S. Pat. No. 3,867,486 attempts to direct air flow substantially uniformly through a surrounding filter pad. U.S. Pat. No. 3,978,174 issued to Peer on Aug. 31, 1976 discloses a typical evaporative cooler apparatus in which an internal motor draws air through the periphery of the apparatus and passes it through a surrounding filter member. Means are provided for splashing water upon the filter member. Air is thus forced by the motor directly down through the center of the apparatus and into peripheral outlets.
Paulus U.S. Pat. No. 2,752,143 includes a central fan unit disposed within a circular shroud of water absorbent material. U.S. Pat. No. 4,798,060 discloses an automotive evaporative air cooler in which the evaporative pad forms the evaporative impeller, and is thus rotated by the fan to force air through the system. A typical generally tubular water pad disposed in encircling relation with respect to a centered fan assembly is seen in U.S. Pat. No. 3,583,174.
A portable evaporative air cooler is seen in F. D. Davidson U.S. Pat. No. 2,769,620. It comprises a generally cylindrical shroud having an interior in which a motor driven fan is concentrically disposed. The fan is disposed within the compartment surrounded by a porous, water excelsior pad through which air is forced by the rotating fan. Air is drawn into the compartment interior through a plurality of vents defined in the periphery of the housing, and it is forced through the pads so that evaporation and humidification occur. The cooled, humidified air is outputted through the top of the apparatus.
U.S. Pat. No. 4,793,152 discloses an evaporative air cooler in which intercommunicating canals and water pathways attempt to precool the air. U.S. Pat. No. 3,348,830 combines evaporative cooling with scrubbing of air. Air to be cleaned is directed through a spiral scrubbing zone where it is subjected to spraying.
Biesemeyer U.S. Pat. No. 4,649,000 issued Mar. 10, 1987 discloses an evaporative cooler which sucks air in through an associated, rotatable generally horizontally disposed chamber. The rotatable, tube like chamber is formed of a water absorbent material, and air drawn through its periphery as it rotates through a water bath is cooled by evaporation through subsequent discharge by a squirrel cage fan.
Another patent which discloses structure relevant to the assembly of evaporative cooler frames and beds is U.S. Pat. No. 4,443,386 issued Apr. 17, 1984. Sealy U.S. Pat. No. 4,338,264 discloses an evaporative air cooler in which a tray like arrangement is employed for handling the water flow to a water pad which covers a squirrel cage fan system.
Less relevant references include U.S. Pat. Nos. 4,043,777; 4,351,781; 4,439,375; 4,752,419; 4,309,365; 3,273,867; 3,698,158; 4,713,943; 3,188,007; 3,365,181; 4,158,679; and 4,774,030.
However, all known prior art evaporative air coolers are relatively inefficient. Inefficiency results from a variety of factors, most notably the internal air path established by the design. Complex air paths result in larger, less portable units. Residential coolers, for example, should be fairly compact and lightweight. And, since typical units must be filled with water often, that task should be made relatively simple. I have discovered a unique internal geometry for evaporative air coolers. By properly positioning a motor system relative to the associated fan within a cage surrounded by a circumferential evaporative pad media, the cage is divided into separate isolated compartments. An air flow path which twice forces air through the water absorbent media results. Motor heat is added to the dry ambient air entering the unit. While compactness is preserved, efficiency is increased and the unit is easy to fill.